Transverse ultra-thin insulated gate bipolar transistor having high current density

ABSTRACT

A transverse ultra-thin insulated gate bipolar transistor having current density includes: a P substrate, where the P substrate is provided with a buried oxide layer thereon, the buried oxide layer is provided with an N epitaxial layer thereon, the N epitaxial layer is provided with an N well region and P base region therein, the P base region is provided with a first P contact region and an N source region therein, the N well region is provided with an N buffer region therein, the N well region is provided with a field oxide layer thereon, the N buffer region is provided with a P drain region therein, the N epitaxial layer is provided therein with a P base region array including a P annular base region, the P base region array is located between the N well region and the P base region, the P annular base region is provided with a second P contact region and an N annular source region therein, and the second P contact region is located in the N annular source region. The present invention greatly increases current density of a transverse ultra-thin insulated gate bipolar transistor, thus significantly improving the performance of an intelligent power module.

FIELD OF THE INVENTION

The present invention relates to power semiconductor devices, and in particular, to a transverse ultra-thin insulated gate bipolar transistor (IGBT) having current density that is integrated on an ultra-thin process platform.

DESCRIPTION OF RELATED ART

Intelligent power modules in high-voltage power integrated circuits can be applied to various fields, for example, driving and controlling various industrial and civil single-phase and three-phase motors. A power switch element in an intelligent power module is a key part in the entire intelligent power module. As a power switch element, an IGBT not only is characterized by a high working speed, large input impedance, and a simple driving circuit of a MOSFET, but also has an advantage of a large current carrying capacity of a bipolar transistor. Therefore, during recent years, IGBTs are frequently used in power integrated circuits. In IGBTs, the L-IGBT attracts our attention as it is suitable to be integrated in a high-density integrated circuit. A large-capacity current output capability is very important in power devices. However, for an ultra-thin L-IGBT, it is very difficult to improve the current density as a conductivity modulation effect is not obvious enough. How to obtain a large current and a high breakdown voltage at a source end and a drain end of the ultra-thin L-IGBT becomes the key to improve the performance of the entire integrated circuit. Therefore, how the ultra-thin L-IGBT functioning as a power switch element obtains high current density undoubtedly is important content of an intelligent power module circuit and process research.

There are already various current density increasing methods for existing L-IGBTs. In the current density increasing methods, a most effective and prominent one is to increase current density of a thick-film L-IGBT in a dual channel manner, which is mentioned in the U.S. Pat. No. 5,731,603 of Toshiba Corporation. In the structure, a P base region has an N epitaxial layer on both sides. Therefore, after a conducting channel is formed on two sides of an N source region, the N epitaxial layer can provide a current flow path. However, in an ultra-thin-film structure, a P base region easily extends to a buried oxide layer below and thus causes an N epitaxial layer that can provide a current flow path to be pinched off. Therefore, the current density increasing method mentioned in the patent U.S. Pat. No. 5,731,603 is impracticable in the ultra-thin structure.

SUMMARY OF THE INVENTION Technical Problem

The present invention provides a transverse ultra-thin IGBT having current density. The present invention solves the problem of low current density of an ultra-thin L-IGBT, and increases current density without reducing a breakdown voltage.

Technical Solution

A transverse ultra-thin IGBT having high current density includes: a P substrate, where the P substrate is provided with a buried oxide layer thereon, the buried oxide layer is provided with an N epitaxial layer thereon, the thickness of the N epitaxial layer is 0.1 to 2 μm, the N epitaxial layer is provided with an N well region and a P base region therein, the N well region is provided with an N buffer region therein, the N well region is provided with a field oxide layer thereon, a boundary of the N buffer region abuts against a boundary of the field oxide layer, the N buffer region is provided with a P drain region therein, and the P base region is provided with a first P contact region and an N source region therein, the N epitaxial layer is provided therein with a P base region array including a P annular base region, the P base region array is located between the N well region and the P base region, the P annular base region is provided with a second P contact region and an N annular source region therein, the second P contact region is located in the N annular source region, a first polysilicon gate is disposed on a surface of a boundary region on which the field oxide layer and the N annular source region are adjacent, the first polysilicon gate extends from the boundary of the field oxide layer towards a direction of the N annular source region to a place above the N annular source region, a first gate oxide layer is disposed below an extension region of the first polysilicon gate, a second polysilicon gate is disposed above the N epitaxial layer, a boundary of the second polysilicon gate extends to the place above the N annular source region, another boundary of the second polysilicon gate extends to a place above the N source region, a second gate oxide layer is disposed below the second polysilicon gate, a dielectric isolation oxide layer is disposed on the field oxide layer, the first polysilicon gate, the second polysilicon gate, the P base region, the P annular base region, the first P contact region, the N source region, the second P contact region, the N annular source region, the N buffer region, and the P drain region, an emitter metal wire is connected to the first P contact region, the N source region, the second P contact region, and the N annular source region, a collector metal wire is connected to the P drain region, and a gate metal wire is connected to the first polysilicon gate and the second polysilicon gate.

Advantageous Effect

Compared with the prior art, the present invention has the following advantages:

The transverse ultra-thin IGBT having high current density of the present invention uses a new structure, that is, the N epitaxial layer (3) is provided therein with the P base region array (17) including the P annular base region (6 b), and the P base region array (17) is located between the N well region (4) and the P base region (6 a). Compared with a conventional transverse ultra-thin IGBT (FIG. 3) having only one P base region, the present invention achieves that after a gate voltage increases constantly, a depletion layer first occurs below the gate oxide layers of the P base region (6 a) and the P annular base region (6 b), and after the gate voltage reaches a threshold voltage, an inversion layer occurs below the gate oxide layers of the P base region (6 a) and the P annular base region (6 b), which is equivalent to addition of a conducting channel of a parasitic NMOS transistor in the transverse ultra-thin IGBT, that is, increase of a current of the parasitic NMOS transistor. As shown in FIG. 1, the N epitaxial layer (3) in the x direction and the y direction further can provide a current flow path, and thus the current of the parasitic NMOS transistor can be used as a base region current of a PNP transistor in the transverse ultra-thin IGBT, so that an electro hole collecting capability is added to the first P contact region (7 a) and the second P contact region (7 b) of the P base region (6 a) and the P annular base region (6 b). Finally, current density of the transverse ultra-thin IGBT is improved.

(2) Because the P base region (6 a) and the P base region array (17) including the P annular base region (6 b) cause increase of a quantity of conducting channels, compared with the conventional transverse ultra-thin IGBT having high current density of the present invention has higher current density under the condition of a same withstand voltage, or has a higher withstand voltage under the condition of same current density.

(3) The transverse ultra-thin IGBT having high current density of the present invention is totally based on an existing transverse ultra-thin IGBT manufacturing process, no additional process step is added, and manufacturing is simple.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a transverse ultra-thin IGBT having high current density according to the present invention;

FIG. 2 is a transverse sectional view along I-I′ line in FIG. 1;

FIG. 3 is a transverse sectional view along II-II′ line in FIG. 1;

FIG. 4 is a transverse sectional view of a structure of a conventional transverse ultra-thin IGBT;

FIG. 5 is a diagram of comparison between current density of a transverse ultra-thin IGBT having high current density (proposed structure) according to the present invention and a conventional transverse ultra-thin IGBT (conventional structure);

FIG. 6 is a diagram of comparison between current density after increase of a line quantity of a P base region array including a P annular base region of a transverse ultra-thin IGBT having high current density according to the present invention;

FIG. 7 is a diagram of comparison between current density after change of a spacing between a P base region and a P annular base region of a transverse ultra-thin IGBT having high current density according to the present invention; and

FIG. 8 is a diagram of comparison between current density after change of a spacing between adjacent boundaries of adjacent P annular base regions of a transverse ultra-thin IGBT having high current density according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, FIG. 2, and FIG. 3, a transverse ultra-thin IGBT having high current density includes: a P substrate 1, where the P substrate 1 is provided with a buried oxide layer 2 thereon, the buried oxide layer 2 is provided with an N epitaxial layer 3 thereon, the thickness of the N epitaxial layer 3 is 0.1 to 1.5 μm, the N epitaxial layer 3 is provided with an N well region 4 and a P base region 6 a therein, the N well region 4 is provided with an N buffer region 5 therein, the N well region 4 is provided with a field oxide layer 11 thereon, a boundary of the N buffer region 5 abuts against a boundary of the field oxide layer 11, the N buffer region 5 is provided with a P drain region 9 therein, and the P base region 6 a is provided with a first P contact region 7 a and an N source region 8 a therein, the N epitaxial layer 3 is provided therein with a P base region array 17 including a P annular base region 6 b, the P base region array 17 is located between the N well region 4 and the P base region 6 a, the P annular base region 6 b is provided with a second P contact region 7 b and an N annular source region 8 b therein, the second P contact region 7 b is located in the N annular source region 8 b, a first polysilicon gate 12 a is disposed on a surface of a boundary region on which the field oxide layer 11 and the N annular source region 8 b are adjacent, the first polysilicon gate 12 extends from the boundary of the field oxide layer 11 towards a direction of the N annular source region 8 b to a place above the N annular source region 8 b, a first gate oxide layer 10 a is disposed below an extension region of the first polysilicon gate 12 a, a second polysilicon gate 12 b is disposed above the N epitaxial layer 3, a boundary of the second polysilicon gate 12 b extends to the place above the N annular source region 8 b, another boundary of the second polysilicon gate 12 b extends to a place above the N source region 8 a, a second gate oxide layer 10 b is disposed below the second polysilicon gate 12 b, a dielectric isolation oxide layer 13 is disposed on the field oxide layer 11, the first polysilicon gate 12 a, the second polysilicon gate 12 b, the P base region 6 a, the P annular base region 6 b, the first P contact region 7 a, the N source region 8 a, the second P contact region 7 b, the N annular source region 8 b, the N buffer region 5, and the P drain region 9, an emitter metal wire 14 is connected to the first P contact region 7 a, the N source region 8 a, the second P contact region 7 b, and the N annular source region 8 b, a collector metal wire 15 is connected to the P drain region 9, and a gate metal wire 16 is connected to the first polysilicon gate 12 a and the second polysilicon gate 12 b.

The P base region array 17 may have multiple lines and multiple columns, and may also have multiple lines and a single line. In this embodiment, a P base region array has one column is selected as the P base region array 17 including the P annular base region 6 b, of which a line quantity is not limited, which may be 2, 3, . . . , 10 or more as long as it is ensured that a spacing between adjacent boundaries of P annular base regions is not changed, that is, a path region on which a current can flow is not changed. Current density is little affected by increase of the line quantity of the P base region array 17 including the P annular base region 6 b.

Refer to FIG. 6 for a diagram of comparison between current density after the increase of the line quantity of the P base region array 17 including the P annular base region 6 b.

In this embodiment, the current density may be further improved by using the following technical measures:

(1) A spacing between adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is 0.5 to 3 μm. If the spacing between the adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is less than 0.5 μm, a region on which a current can flow is excessively small, the current density can be improved but the effect is not obvious. If the spacing between the adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is greater than 3 μm, a current flow path is excessively long, and the current density can also be improved but the effect is not obvious. Refer to FIG. 7 for a diagram of comparison between current density after change of the spacing between the adjacent boundaries of the P base region (6 a) and the P annular base region (6 b).

(2) A spacing between adjacent boundaries of adjacent P annular base regions is 1 to 6 μm. If the spacing between the adjacent boundaries of the adjacent P annular base regions is less than 1 μm, a region on which a current can flow is excessively small, the current density can be improved but the effect is not obvious. If the spacing between the adjacent boundaries of the adjacent P annular base regions is greater than 6 μm, and the current density can also be improved but the effect is not obvious. Refer to FIG. 8 for a diagram of comparison between current density after change of the spacing between the adjacent boundaries of the adjacent P annular base regions.

The present invention uses the following method for manufacturing:

1. Select and clean a P silicon substrate, deposit an oxide layer, then perform epitaxy, silicon nitride deposition, photo etching, and ion implantation to phosphorous to generate an N well region, and perform annealing, silicon nitride removal, photo etching, and ion implantation to boron to generate a P base region and a P annular base region.

2. Implant ions to arsenic and phosphorous to generate an N buffer region, perform silicon nitride deposition and photo etching to form an active region, etch silicon nitride, then perform field oxide growth and field implantation, adjust a channel threshold voltage, then perform gate oxide layer growth, deposit and etch polysilicon to form a first polysilicon gate, a second polysilicon gate, and a polysilicon field plate, perform source and drain implantation to form an N source region, an N annular source region, a first P contact region, a second P contact region, and a P drain region, and then deposit a field oxide layer.

3. Etch the field oxide layer to form metal electrode lead-out holes of the N source region, the N annular source region, the first P contact region, the second P contact region, the first polysilicon gate, the second polysilicon gate, and the P drain region, deposit a metal layer, and etch the metal layer to form lead-out electrodes of the N source region, the N annular source region, the first P contact region, and the second P contact region of the transverse ultra-thin IGBT, lead-out electrodes of the first polysilicon gate and the second polysilicon gate, and a lead-out electrode of the P drain region. Finally, perform passivation processing. 

1. A transverse ultra-thin insulated gate bipolar transistor having high current density, comprising: a P substrate (1), wherein the P substrate (1) is provided with a buried oxide layer (2) thereon, the buried oxide layer (2) is provided with an N epitaxial layer (3) thereon, the thickness of the N epitaxial layer (3) is 0.1 to 1.5 μm, the N epitaxial layer (3) is provided with an N well region (4) and a P base region (6 a) therein, the N well region (4) is provided with an N buffer region (5) therein, the N well region (4) is provided with a field oxide layer (11) thereon, a boundary of the N buffer region (5) abuts against a boundary of the field oxide layer (11), the N buffer region (5) is provided with a P drain region (9) therein, and the P base region (6 a) is provided with a first P contact region (7 a) and an N source region (8 a) therein, wherein the N epitaxial layer (3) is provided therein with a P base region array (17) comprising a P annular base region (6 b), the P base region array (17) is located between the N well region (4) and the P base region (6 a), the P annular base region (6 b) is provided with a second P contact region (7 b) and an N annular source region (8 b) therein, the second P contact region (7 b) is located in the N annular source region (8 b), a first polysilicon gate (12 a) is disposed on a surface of a boundary region on which the field oxide layer (11) and the N annular source region (8 b) are adjacent, the first polysilicon gate (12) extends from the boundary of the field oxide layer (11) towards a direction of the N annular source region (8 b) to a place above the N annular source region (8 b), a first gate oxide layer (10 a) is disposed below an extension region of the first polysilicon gate (12 a), a second polysilicon gate (12 b) is disposed above the N epitaxial layer (3), a boundary of the second polysilicon gate (12 b) extends to the place above the N annular source region (8 b), another boundary of the second polysilicon gate (12 b) extends to a place above the N source region (8 a), a second gate oxide layer (10 b) is disposed below the second polysilicon gate (12 b), a dielectric isolation oxide layer (13) is disposed on the field oxide layer (11), the first polysilicon gate (12 a), the second polysilicon gate (12 b), the P base region (6 a), the P annular base region (6 b), the first P contact region (7 a), the N source region (8 a), the second P contact region (7 b), the N annular source region (8 b), the N buffer region (5), and the P drain region (9), an emitter metal wire (14) is connected to the first P contact region (7 a), the N source region (8 a), the second P contact region (7 b), and the N annular source region (8 b), a collector metal wire (15) is connected to the P drain region (9), and a gate metal wire (16) is connected to the first polysilicon gate (12 a) and the second polysilicon gate (12 b).
 2. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein the P base region array (17) comprising the P annular base region (6 b) is a P base region array having one column.
 3. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein the P annular base region (6 b) is hexagonal, quadrilateral, or circular.
 4. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein a spacing between adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is 0.5 to 3 μm.
 5. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein a spacing between adjacent boundaries of adjacent P annular base regions (6 b) is 1 to 6 μm.
 6. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 2, wherein the P annular base region (6 b) is hexagonal, quadrilateral, or circular. 